It is desirable to be able to completely power down a device when it is not in use or when it is disabled. For example, a notebook computer may have a wired LAN adapter and a wireless LAN adapter installed. When the notebook computer is moved from one location to another, the wireless LAN adapter may be used, for example, when there is no wired LAN available. As a result, the wired LAN adapter may not be needed. Accordingly, the wired LAN adapter may be disabled to reduce power consumption, which conserves battery power.
Some conventional systems may configure the wired LAN adapter to operate in a power down state by disabling clock signals, turning off transceivers, and/or configuring analog devices to operate in a standby state. However, there may still be some current drawn from a power supply. For example, a network adapter device (NAC) may have three primary supply voltages: 1.2V, 2.5V, and 3.3V. When the NAC is configured to operate in the power down state by asserting, for example, a LOW_POWER_MODE pin, the lowest measured current may be, for example, about 27 mA. This may translate to over 100 mW of power consumption during the power down state when the current is regulated down from the 5V supply in the system.
The NAC may derive the other supply voltages of 2.5V and 1.2V from the 3.3V supply voltage. In order to avoid this power drain from the 2.5V and 1.2V supply voltages, as well as from the 3.3V supply voltage, some conventional systems may turn off the 3.3V supply to the NAC. A disadvantage with this approach may be that turning off the 3.3V supply voltage to the NAC may affect long-term reliability of the NAC because it may stress damage the I/O cells in the NAC. This may also lead to leakage current through the non-powered I/O cells to which the NAC may be coupled. The resulting power drain at the system level may be greater than if the 3.3V supply voltage to the NAC was not turned off.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.